Energy attenuation restrictor device and method of forming such restrictor device

ABSTRACT

An energy attenuation restrictor device for use in an energy attenuation apparatus for a conduit adapted to convey a liquid under pressure, particularly, in the power steering system of a vehicle wherein said energy attenuation restrictor device includes a tuning cable composed of a first organic polymer and a fitting member composed of a second organic polymer, and a method for molding the energy attenuation restrictor device are described.

BACKGROUND OF THE INVENTION

[0001] This invention relates to energy attenuation apparatus and moreparticularly to a new energy attenuation restrictor device for use in anenergy attenuation apparatus adapted to convey liquid under pressure forthe attenuation of pressure pulsations in the liquid and to a method formanufacturing a restrictor device. The restrictor device of theinvention is especially useful in the energy attenuation apparatus ofthe hydraulic system of a power steering unit of a vehicle. Theinvention would also be suitable for other hydraulic systems.

[0002] In hydraulic systems where the operating liquid is circulated bya pump, the pulsations of pressure generated by the pump are transmittedthrough the conduits and result in noise and/or vibration being producedby the hydraulic liquid. In the case of power steering fluid invehicles, such noise and/or vibration are caused, for example, when avehicle is being operated at idle or very low speeds of movement such asbarely moving into and out of a parking space where the wheels of thevehicle are being turned by the power steering mechanism. In thoseinstances where the wheels are being turned with little or no rolling ofthe wheel, substantial noise and/or vibration (shudder) can be producedwhen the power steering fluid passes through the power steeringmechanism from the power steering pump to the effective steeringstructure. Further background in this area can be found in U.S. Pat. No.3,323,305 to Klees which is incorporated herein by reference thereto.

[0003] Devices are known for suppressing noise in exhaust gas mufflers.For example, U.S. Pat. No. 4,501,341 to Jones provides two side branchresonators, while U.S. Pat. No. 4,371,053 to Jones provides an aperturedtube in a gas muffler housing. Systems are also known for controllingthe resonation of pressure waves in fuel injection systems. Forexamples, U.S. Pat. No. 5,168,855 to Stone passes fluid through checkvalves that are provided with a flow restriction either directly thereinor in a bypass line. U.S. Pat. No. 5,509,391 to DeGroot provides a spoolvalve assembly for controlling flow between inlet and outlet ports.Henderson et al., in U.S. Pat. No. 4,671,380, discloses a long andnarrow tubular casing having a perforated tube extending therethrough.Finally, “Acoustics of Ducts and Mufflers”, by M. L. Munjal, describesan apertured resonator tube disposed in a tubular cavity for conveyinggas.

[0004] Commonly assigned U.S. Pat. Nos. 6,073,656 and 6,123,108, both toChen et al., the contents of which are incorporated herein by referencethereto, describe energy attenuation apparatus providing tubular meanshaving an inlet opening for receiving liquid from the system, and anoutlet opening for returning the liquid to the system, wherein an inletconduit extends concentrically into the tubular means through the inletopening such that an annular space is formed between the inlet conduitand the tubular means. In a portion of the inlet conduit disposed in thetubular means, the inlet conduit is provided with at least one aperturefor introducing liquid from the inlet conduit into the annular spacebetween the inlet conduit and the tubular means.

[0005] Applicants are not aware of any other teaching of transferringflow of liquid under pressure from one tube to another as a means ofsuppressing energy, especially where at least one of the tubes isprovided with at least one hole.

SUMMARY OF THE INVENTION

[0006] It is an object of the present invention to provide an improvedenergy attenuation restrictor device for attenuating energy in a conduitthat conveys liquid under pressure.

[0007] It is another object of the invention to provide a method formanufacturing an improved energy attenuation restrictor device forattenuating energy in a conduit that conveys liquid under pressure.

[0008] In a pressurized liquid system, such as a power steering systemin an automobile, pressurized liquid is generated and transmittedthrough tubing, such as steel tubing, to a pressure line, a powersteering gear, a fluid return line, a reservoir and finally back to thepump itself. During the generation and transmission of the fluid underpressure, pressure ripples are also generated and transmitted throughthe tubing. In order to reduce such pressure ripples before they reachthe gear, and thereby eliminate or at least greatly reduce the powersteering noise or vibration generated by the power steering pump, anenergy attenuation device such as that described in the above commonlyassigned U.S. Pat. Nos. 6,073,656 and 6,123,108 to Chen et al., isdisposed in the pressure line between the power steering pump and thegear.

[0009] Currently, the restrictor device for attenuating energy, commonlyreferred to a tuning cable assembly, consists of a tuning cable whichmay be constructed of a metal or a polymeric material, and a metalfitting member annularly disposed around one end of the tuning cable andheld in place by friction. This fitting member including the tuningcable is inserted into a metal support member which is crimped to holdthe fitting member and the tuning cable in place in the metal supportmember. The tuning cable assembly anchored to the metal member is theninserted into a housing or, preferably a hose and kept in place by ametallic shell which is crimped onto the hose.

[0010] In the present invention, both the tuning cable and the fittingmember of the restrictor device are manufactured from a polymericmaterial. Both parts may be made of the same plastic material or theymay be made from different plastic materials. By using polymericmaterials to manufacture both the tuning cable and the fitting member inaccordance with the present invention, the inventive restrictor deviceis more conveniently recyclable, lower in cost, lighter in weight, and,more importantly, consists of fewer parts. In a particularly preferredand advantageous embodiment of the invention, the present restrictordevice is manufactured in a single step in an injection molding machinewherein the tuning cable and the fitting member, are simultaneouslymolded together forming a unitary restrictor device.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011]FIG. 1 is a sectional view of an exemplary energy attenuationapparatus containing a prior art restrictor device;

[0012]FIG. 2 is a sectional view of an energy attenuation assemblycontaining one embodiment of a restrictor device of the presentinvention;

[0013]FIG. 3 is a sectional view of an energy attenuation assemblycontaining another embodiment of restrictor device of the presentinvention;

[0014]FIG. 4 illustrates a power steering system utilizing an energyattenuation apparatus containing a restrictor device of the presentinvention; and

[0015]FIG. 5 illustrates a schematic diagram of a molding process forthe manufacture of a restrictor device of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

[0016] One aspect of the invention is a new restrictor device for use inan energy attenuation apparatus which not only reduces the number ofparts needed to construct the restrictor device, but also provides adevice which is lighter in weight, lower in cost, easier to manufactureand recycle than prior art restrictor devices.

[0017] Another aspect of the invention is a method for the manufactureof the restrictor device which allows the device to be constructed as asingle unit or from separate parts.

[0018] Still another aspect of the invention is in the use of the newrestrictor device of the present invention to attenuate energy in aconduit adapted to convey a liquid under pressure.

[0019] In accordance with the invention, both the tuning cable and thefitting member of the energy attenuation apparatus of an automobilepower steering system are constructed from polymeric materials. Thepolymeric materials may or may not be similar in composition. If thematerials used to construct the tuning cable and the fitting member arenot the same or at least similar in composition, or if they areincompatible, it will be necessary to provide a means for securing thefitting member and the tuning cable together. Preferably the tuningcable and the fitting member are constructed from polymeric materialswhich are similar in composition or have the same composition, or arecompatible.

[0020] The energy attenuation restrictor device of this invention islighter in weight; lower in cost; consists of fewer parts; and is moreconveniently recyclable than the attenuation restrictor devicespresently in use in the industry. In addition to the above advantages,the present attenuation restrictor device can be convenientlymanufactured in a single molding process, depending upon the particularpolymeric materials used to manufacture the restrictor device.

[0021] Referring now to the drawings in detail, FIG. 1 illustrates aprior art restrictor device 10 for attenuating energy. The restrictordevice 10 consists of a tuning cable 12 which may be constructed of ametal or a polymeric material, and a metal fitting member 14 annularlydisposed around one end of the tuning cable 12 to form a tuning cableassembly 16. The tuning cable 12 and metal fitting member 14 are held inplace by friction. The tuning cable assembly 16 is inserted into a metalsupport member 18 which is crimped to hold the metal fitting member 14and the tuning cable 12 in place in the metal support member 18. Themetal tuning cable assembly 16 anchored to the metal support member 18is then inserted into a rubber hose 20 and kept in place by a metallicshell 22 which is crimped onto the hose 20. A narrow annular space 24 offrom about {fraction (1/32)} to ⅜ of an inch or longer is formed betweenthe outer periphery of the tuning cable 12 and the inner periphery ofthe hose 20. The narrow annular space 24 is formed to receive hydraulicfluid from the tuning cable 12 via one or more apertures 26 in thetuning cable 12. The distance between the outer periphery of the tuningcable 12 and the inner periphery of the hose 20 forming the annularspace 24 is about {fraction (1/32)} to ⅜ of an inch. Various otherembodiments and configurations of the energy attenuation apparatus andcomponents and arrangements thereof are described in commonly assignedU.S. Pat. Nos. 6,073,656 and 6,123,108, the contents thereof beingincorporated herein by reference thereto.

[0022]FIG. 2 represents one embodiment of the present invention whichconsists of a restrictor device 100 wherein the tuning cable 102 ismolded over by the polymeric fitting 104, e.g., in an injection moldingmachine or transfer molding. In this embodiment, different materials maybe employed to manufacture the tuning cable 102 and the polymericfitting member 104. If the materials are different or not compatible, itmay be necessary to form one or more locking structures 106 in or oneither the tuning cable 102-or the fitting 104. For example, where thematerials have a different melting point, one of the parts such as thetuning cable 102 can be constructed from the material having the highermelting point and the fitting member 104 can be formed from a materialhaving the lower melting point. In this case the tuning cable 102 formedfrom the higher melting polymer would be formed with one or more lockingstructures therein, and the fitting member 104 constructed from thelower melting polymer typically would be molded over the tuning cable102 so that the lower melting polymeric material would flow into oraround the locking structures 106, thereby permanently securing thetuning cable 102 to the fitting member 104. As shown in FIG. 2, thelocking structure 106 is illustrated as being in the form of a holeformed in the tuning cable 102 constructed from a relatively highmelting polymeric material. As the fitting member 104, constructed froma relatively low melting polymeric material, is molded over the lockingstructure 106 the lower melting polymeric material fills the hole and,upon cooling, forms a solid pin therein to lock the tuning cable 102 andthe fitting member 104 together. The locking structures 106 may be ofany configuration, e.g., a depression such as one or more circularholes, oval holes, elongated slots, grooves, or the locking structuremay be a protrusion such as one or more pins, rods, etc.

[0023]FIG. 3 represents another embodiment of the restrictor device 200of the present invention wherein the tuning cable 202 and the polymericfitting member 204 are constructed from the same material. Because thetwo parts are constructed from the same material, they can be moldedsimultaneously in a single molding apparatus such as by injectionmolding, wherein the tuning cable 202 and the fitting member 204 areformed as the unitary restrictor device 200.

[0024] The tuning cable and the fitting member making up the restrictordevice of the present invention may be fabricated from any knownpolymeric material which is compatible with the conditions of theintended use of the restrictor device. For example, if the restrictordevice is employed in a system requiring high temperatures and/orpressure, the polymeric material must be capable of withstanding suchhigh temperatures and/or pressures. Furthermore, the polymeric materialmust be inert with respect to the atmosphere in which it is used, andresistant to any chemicals that it may contact. Typically the parts ofthe restrictor device 200 are constructed from high melting polymericmaterials, e.g., polyamides, such as nylons; and halogenated hydrocarbonpolymers, such as teflon. Preferably, both the tuning cable and thefitting member are constructed from compatible polymeric materials suchas nylons, e.g., 6,6 nylon; glass filled nylon 6,6; nylon 6; glassfilled nylon 6; nylon 4,6; glass filled nylon 4,6; nylon 11 and glassfilled nylon 11, etc. However, in certain applications where the deviceis used to circulate fluid or gas at a relatively low temperature, e.g.,room temperature or slightly above room temperature, other lower meltingpolymeric materials such as polyolefins, e,g., polyethylene, highdensity polyethylene (HDPE), ultra high density polyethylene (UHDPE),polypropylene; polyesters, polyurethanes or thermoplastic elastomershaving elongation at break more than 15% etc. may be employed to formeither the tuning cable 202 or the fitting member 204 or both.

[0025] The structures of FIGS. 2 and 3 are further illustrated asexhibiting multiple annular ridges on the outer surface of the polymericfitting member to provide a ripple-like effect. These annular ridgesexhibit an irregular surface which, when in contact with the rough innersurface of the rubber hose, improves surface contact between the twosurfaces and improves pull-off resistance. Furthermore, the annularridges provide increased structural strength of the filling member. InFIG. 2, multiple annular ridges 108 and annular valleys 110 are shown onthe outer surface of polymeric fitting member 104 for gripping theirregular inner surface 112 of rubber hose 120 when assembled thereto.In a similar manner, the embodiment of FIG. 3 also includes a pluralityof annular ridges 208 and annular valleys 210 on the outer surface ofpolymeric fitting member 204 for gripping the irregular inner surface212 of rubber hose 200. These ridges and valleys are illustrated asbeing annular along the axis of the respective restrictor devices;however, other configurations are possible such as protrusions andindentations, and the like. The number of annular ridges and annularvalleys formed on the outer surface of the polymeric fitting members isnot critical as long as the ridges and valleys provide adequate grippingcharacteristics to prevent the fitting member from being pulled out ofthe hose and adequate strength to the part.

[0026] While, as shown in FIGS. 2 and 3, the energy attenuation devicesof the present invention (100, 200) generally include one or moreapertures (126, 226) in the tuning cable (102, 202) and a narrow annularspace (124, 224) formed between the outer periphery of the tuning cable(102, 202) and the inner periphery of the hose (120, 220) for receivinghydraulic power steering fluid from the tuning cable (102, 202) throughthe apertures (126, 226), the present energy attenuation devices (100,200) do not need the metal support member which is required in the priorart energy attenuation devices.

[0027]FIG. 4 illustrates a simplified automotive power steering systemS. During operation, the power steering pump 310 generates pressureripples that are transmitted through tubing, such as steel tubing, tothe pressure line 312, the power steering gear 314, the return line 316,and the reservoir 318, and finally flow back to the pump 310 itself bymeans of the supply line 320. In accordance with the present invention,a proposed power steering system utilizes the new restrictor device ofthe present invention to greatly reduce such pressure ripples beforethey reach the power steering gear 314 via the pressure line 312. Thenew energy attenuation restrictor device as shown in FIGS. 2 and 3, butnot shown in FIG. 4 of the present invention is disposed in the pressureline 312 between the pump 310 and the gear power steering gear 314.

[0028] An apparatus for constructing a restrictor device 400 of thepresent invention is shown in schematic form in FIG. 5 wherein aninjection molding machine M is used to mold either or both of thepolymeric tuning cable 400 and the polymeric fitting member 414. In oneembodiment of the invention, the polymeric tuning cable and thepolymeric fitting member 414 are molded separately and then fittedtogether in a separate step. In this embodiment, it may be necessary toprovide a means for adhering the two parts together. One such meanswould be to use an adhesive which is compatible with both of the moldedparts. Alternatively, one of the two parts is formed with one or moreapertures and the second part is then over molded on the first part suchthat the molten material of the second part, having a lower meltingpoint than that of the first part, would flow into the aperture(s) inthe first part and lock the two parts together upon cooling. Therestrictor device formed in accordance with this invention isillustrated in FIG. 2. In a preferred method of manufacturing therestrictor device of the invention, both the tuning cable and thefitting member are constructed from the same, or at least similar orcompatible, polymeric materials. The restrictor device in accordancewith this embodiment of the invention is illustrated in FIG. 3.

[0029] While the restrictor device and the methods for constructing andusing the energy attenuation restrictor device of the present inventionhave been illustrated and described, it is to be understood that aperson having ordinary skill in the art will recognize other materialsand method steps which can be utilized in the manufacture and use ofenergy attenuation restrictor devices without departing from the scopeof the appended claims.

What is claimed is:
 1. An energy attenuation restrictor device for usein an energy attenuation apparatus adapted to convey a liquid underpressure for the attenuation of pressure pulsations in the liquid,comprising: a tuning cable composed of an organic polymer, said tuningcable comprising a tubular wall structure having an inner surface and anouter surface, and a fitting member composed of an organic polymer, saidfitting member comprising a tubular wall structure having an innersurface and an outer surface wherein said fitting member is disposed onone end of said tuning cable such that an inner surface of fittingmember is adjacent to or continuous with said outer surface of saidtuning cable, said tuning cable and said fitting member being fabricatedfrom an organic polymer possessing characteristics such that said deviceis compatible with the environment in which it is employed.
 2. Theenergy attenuation restrictor device of claim 1 wherein said tuningcable is composed of an organic polymer selected from the groupconsisting of polyamides, halogenated hydrocarbon polymers, polyolefinsand polyesters, polyurethanes and thermoplastic elastomers havingelongation at break more than 15%.
 3. The energy attenuation restrictordevice of claim 2 wherein said tuning cable is composed of a polyamide.4. The energy attenuation restrictor device of claim 3 wherein saidpolyamide is nylon.
 5. The energy attenuation restrictor device of claim4 wherein said nylon is selected from the group consisting of nylon 6,6;glass filled nylon 6,6; nylon 6; glass filled nylon 6; nylon 4,6; andglass filled nylon 4,6.
 6. The energy attenuation device of claim 5wherein said nylon is nylon 6,6 or glass filled nylon 6,6.
 7. The energyattenuation restrictor device of claim 1 wherein said fitting member iscomposed of an organic polymer selected from the group consisting ofpolyamides, halogenated hydrocarbon polymers, polyolefins, polyesters,polyurethanes and thermoplastic elastomers having elongation at breakmore than 15%.
 8. The energy attenuation restrictor device of claim 7wherein said fitting member is composed of a polyamide.
 9. The energyattenuation restrictor device of claim 8 wherein said polyamide isnylon.
 10. The energy attenuation restrictor device of claim 9 whereinsaid nylon is nylon 6,6; glass filled nylon 6,6; nylon 6; glass fillednylon 6; nylon 4,6; and glass filled nylon 4,6.
 11. The energyattenuation restrictor device of claim 10 wherein said nylon is nylon6,6 or glass filled nylon 6,6.
 12. The energy attenuation restrictordevice of claim 1 wherein said fitting member further includes grippingand strengthening means on the outer surface thereof to enhance pull-offresistance of said energy attenuation restrictor device from a hose inwhich said energy attenuation restrictor device is fitted and to provideenhanced strength thereto.
 13. The energy attenuation restrictor deviceof claim 12 wherein said gripping means includes a plurality of annularridges on the outer surface of said fitting member.
 14. The energyattenuation restrictor device of claim 1 wherein said tuning cable andsaid fitting member are composed of incompatible polymeric materials,said tuning cable and said fitting member being secured to each other byan adhesive.
 15. The energy attenuation restrictor device of claim 1wherein said tuning cable and said fitting member are composed ofincompatible polymeric materials, said tuning cable and said fittingmember being secured to each other by forming one of said tuning cableand said fitting member from a first polymeric material having a firstmelting point and forming the other of said tuning cable and saidfitting member from a second polymeric material having a second meltingpoint, said first polymeric material exhibiting a melting pointdifferent from the melting point of said second polymeric materialwherein a locking member is formed in the polymeric material having ahigher melting point.
 16. The energy attenuation restrictor device ofclaim 15 wherein said locking member is an aperture or a protrusion andsaid polymeric material having a lower melting point flows into saidaperture or around said protrusion upon constructing said restrictordevice such that, upon cooling said device, the first and secondpolymeric materials are locked together.
 17. The energy attenuationrestrictor device of claim 1 wherein said tuning cable and said fittingmember are composed of compatible polymer materials, said tuning cableand said fitting member being constructed to form a molded unitarydevice.
 18. The energy attention restrictor device of claim 1 whereinsaid energy attenuation restrictor device is constructed in an injectionmolding apparatus.
 19. The energy attenuation restrictor device of claim1 wherein said energy attenuation restrictor device is connected to saidpressure line in a power steering system of a vehicle.
 20. The energyattenuation restrictor device of claim 19 wherein said energyattenuation restrictor device is connected to said pressure line betweena power steering pump and a power steering gear.
 21. An energyattenuation restrictor device for use in an energy attenuation apparatusfor the attenuation of pressure pulsations in the liquid in a powersteering system of a vehicle wherein the energy attenuation restrictordevice is molded in an injection molding apparatus as a unitarystructure, comprising: a tuning cable composed of a nylon or a glassfilled nylon, said tuning cable comprising a tubular wall structurehaving an inner surface and an outer surface, and a fitting membercomposed of a nylon or a glass filled nylon, said fitting membercomprising a tubular wall structure having an inner surface and an outersurface, said outer surface of said fitting member further including aplurality of ridges thereon to improve structural strength of saidfitting member and enhance pull-off resistance of said fitting memberfrom a hose in which said energy attenuation restrictor device isfitted, said fitting member being disposed on one end of said tuningcable such that an inner surface of fitting member is adjacent to orcontinuous with said outer surface of said tuning cable.
 22. A methodfor manufacturing an energy attenuation restrictor device containing apolymeric tuning cable and a polymeric fitting member, wherein saidrestrictor device is used in an energy attenuation apparatus for theattenuation of pressure pulsations in the liquid employed in a powersteering system in a vehicle, comprising: selecting a first polymericmaterial for use in constructing said tuning cable, said first polymericmaterial having characteristics such that the tuning cable fabricatedtherefrom is compatible with an environment in which said tuning cableis employed; molding said tuning cable in an injection molding machine;selecting a second polymeric material for use in constructing saidfitting member, said second polymeric material having characteristicssuch that the tuning cable fabricated therefrom is compatible with anenvironment in which said tuning cable is employed; and molding saidfitting member from said second polymeric material in an injectionmolding machine.
 23. The method of claim 22 wherein said first polymericmaterial is a nylon or glass filled nylon and said second polymericmaterial is nylon or glass filled nylon and said tuning cable and saidfitting member are molded simultaneously in an injection molding machineto form a single unitary energy attenuation restrictor device.
 24. Themethod of claim 22 wherein said first polymeric material has a firstsoftening or melting point and said second polymeric material has asecond softening or melting point, the softening or melting point ofsaid first polymeric material being different from the softening ormelting point of said second polymeric material, and said tuning cableand said fitting member are molded individually in aid injection moldingmachine to form a separate tuning cable and a separate fitting member.25. The method of claim 24 wherein said molded tuning cable is a tubularstructure having an inner diameter and an outer diameter, and saidmolded fitting member is a tubular structure having an inner diameterand an outer diameter, the inner diameter of said fitting member beingof sufficient diameter to accept said tuning cable and the outerdiameter of said tuning cable being of sufficient size to allow saidtuning cable to be inserted into said fitting member, such that saidtuning cable and said fitting member can be securely connected to eachother.
 26. The method of claim 25 further including the steps of:molding said tuning cable to include one or more depressions in theouter surface thereof; molding said fitting member; inserting one end ofsaid tuning cable into one end of said fitting member; and using saidlocking means to secure said fitting member to said tuning cable. 27.The method of claim 26 wherein said one or more depressions are in theform of indentations, holes or annular grooves in the outer surface ofsaid tuning cable.
 28. The method of claim 26 wherein said fittingmember is molded over said tuning cable in an injection molding machinesuch that said second polymeric material flows into said indentationswhereby said fitting member is secured to said tuning cable upon coolingsaid energy attenuation restrictor device.
 29. The method of claim 26wherein said fitting member is fitted over said tuning cable and heatedto a temperature at or higher than the softening point or melting pointof said second polymeric material, and lower than the softening point ormelting point of said first polymeric material whereby said fittingmember is secured to said tuning cable upon cooling said energyattenuation restrictor device.
 30. In restrictor device for use in anenergy attenuation apparatus in a conduit adapted to convey a liquidunder pressure for the attenuation of pressure pulsations in the liquidemployed in a power steering system in a vehicle wherein said restrictorcontains a tuning cable, a fitting member and a metal support member forproviding structural stability and strength to said restrictor device,the improvement of which comprises forming a unitarily formed energyattenuation restrictor device having polymeric tuning cable and apolymeric fitting member, said polymeric fitting member having aplurality of annular ridges formed on the outer surface thereof toimprove structural strength of said fitting member and to provideenhanced pull off resistance to said restrictor device wherein saidpolymeric tuning cable and said polymeric fitting member are formed fromthe same or compatible polymeric materials having the same or similarmelting points, said polymeric tuning cable and said polymeric fittingmember being molded simultaneously in an injection molding machine toform a molded unitary energy attenuation restrictor device.
 31. Therestrictor device of claim 30 wherein said polymeric tuning cable andsaid polymeric fitting member are formed from a polyamide.
 32. Therestrictor device of claim 31 wherein said polyamide is nylon or glassfilled nylon.